One theory is that the blow-up (2) is the original from the TNG Movies Sketchbook, and that someone (maybe even I myself) corrected the deflector placement (1) which was too high on (2). I posted (1) a long time ago, and when I later looked for a larger version I found (2), thinking it was exactly the same.

It's really difficult to find a clear shot of the MSD from the film itself that isn't either obscured by a person or too far away to be seen clearly, but to my eyes, it looks like the MSD in the film matches the one above with the incorrectly placed deflector dish and the warp core that goes all the way to the bottom of the engineering hull:

So it looks like someone recognized that the MSD from the movie was wrong, and then changed it up a bit for the "Generations and First Contact Sketchbook."

It's clear that it must have been a correction rather than a new design by the fact that unlike all other ships, the warp core in the Sketchbook MSD doesn't have a way to eject out of the bottom of the ship. This is because they had to rearrange things to fit the deflector in the correct place.

On another note, the elevator leading up to the saucer aft shuttlebay is a deck higher than it was in the movie MSD, and the shuttles are removed from the image, which is probably because in the movie we only see a Workbee leave from that neck mounted square portal.

with the incorrectly placed deflector dish and the warp core that goes all the way to the bottom of the engineering hull

That was exactly my reason to assume that the incorrect version is the original.

In the meantime I discovered that in (1) there is a hull cut-out right in front of where the deflector dish is on (2). In other words, someone moved the deflector dish but not the cut-out to the correct position.